Ionization from Heated Platinum, 



185 



and of a second substance giving maximum ionization after 

 2 to 6 minutes' heating under potential depending upon 

 the temperature used. At the higher temperature (765° C, 

 fig. 5, and 774° C, fig. 4) this secondary rise of positive 

 currents with time is not much, if at all, in evidence. This 

 is to be expected since with increase of temperature the 

 decay constant of the second substance changes with 

 temperature ; the higher the temperature the more rapid 

 the rise of current to the intermediate maximum. This 

 second maximum would therefore be masked by the rela- 

 tively large initial ionization currents due to the first source 



Fig. 5. 



Tint - /icau.T«v 



producing ions. An analysis of such curves can be made 

 in a manner similar to that given by Rutherford in his 

 * Radioactive Substances and their Transformations,' p. 438. 

 The plate taken from the above reference is given in the 

 right hand portion of fig. 4. Such a curve as No. 3, fig. 4, 

 may be analysed into two current-time relations, the first 

 being expressible by V = n^e~^ yt and the second by the 

 equation 



^•3 — *"2 



Any attempts at details seems superfluous here, since the 

 decay constants \ b X 2 , and \ 3 vary with the temperature. 

 Of course the interpretation to be given figs. 4 and 5 is not 

 the same as that given in radioactive analysis, since we are 

 presumably dealing here with two distinct sources of ions 

 and not with a succession of changes from A to B to C. 



